Choose Athletic as supermax, Samoht. For sure, it's the easiest skill in the game. Yup, it is. Just go to the gym, have your Sim work out, then wait till fatigue is gone (best to go to gym before work, or sleep). While trying to complete the Skill Journal challenges, don't be surprised if you already max the skill. Challenges are easy too. Most of my Sims halfway complete it when trying to max the skill. Martial Arts is a LOT harder. Certainly not recommended. But, if you want lots of money, it might be worth, just for space rocks and stuff. Only downside of Athletic is that you can't improve it until the Sim is T/YA (don't exactly remember). Some skills are way faster: Painting, Logic, and Writing. All of those can be improved starting from the child stage.